/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.read.reader;

import org.apache.iotdb.tsfile.utils.ReadWriteForEncodingUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ClosedByInterruptException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;

public class LocalTsFileInput implements TsFileInput {

    private static final Logger logger = LoggerFactory.getLogger(LocalTsFileInput.class);

    private final FileChannel channel;
    private final String filePath;

    public LocalTsFileInput(Path file) throws IOException {
        channel = FileChannel.open(file, StandardOpenOption.READ);
        filePath = file.toString();
    }

    @Override
    public long size() throws IOException {
        try {
            return channel.size();
        } catch (IOException e) {
            logger.error("Error happened while getting {} size", filePath);
            throw e;
        }
    }

    @Override
    public long position() throws IOException {
        try {
            return channel.position();
        } catch (IOException e) {
            logger.error("Error happened while getting {} current position", filePath);
            throw e;
        }
    }

    @Override
    public TsFileInput position(long newPosition) throws IOException {
        try {
            channel.position(newPosition);
            return this;
        } catch (IOException e) {
            logger.error("Error happened while changing {} position to {}", filePath, newPosition);
            throw e;
        }
    }

    @Override
    public int read(ByteBuffer dst) throws IOException {
        try {
            return channel.read(dst);
        } catch (ClosedByInterruptException e) {
            logger.warn(
                    "Current thread is interrupted by another thread when it is blocked in an I/O operation upon a channel.");
            return -1;
        } catch (IOException e) {
            logger.error("Error happened while reading {} from current position", filePath);
            throw e;
        }
    }

    @Override
    public int read(ByteBuffer dst, long position) throws IOException {
        try {
            return channel.read(dst, position);
        } catch (ClosedByInterruptException e) {
            logger.warn(
                    "Current thread is interrupted by another thread when it is blocked in an I/O operation upon a channel.");
            return -1;
        } catch (IOException e) {
            logger.error("Error happened while reading {} from position {}", filePath, position);
            throw e;
        }
    }

    @Override
    public int read() {
        throw new UnsupportedOperationException();
    }

    @Override
    public int read(byte[] b, int off, int len) {
        throw new UnsupportedOperationException();
    }

    @Override
    public FileChannel wrapAsFileChannel() {
        return channel;
    }

    @Override
    public InputStream wrapAsInputStream() {
        return Channels.newInputStream(channel);
    }

    @Override
    public void close() throws IOException {
        try {
            channel.close();
        } catch (IOException e) {
            logger.error("Error happened while closing {}", filePath);
            throw e;
        }
    }

    @Override
    public int readInt() {
        throw new UnsupportedOperationException();
    }

    @Override
    public String readVarIntString(long offset) throws IOException {
        try {
            ByteBuffer byteBuffer = ByteBuffer.allocate(5);
            channel.read(byteBuffer, offset);
            byteBuffer.flip();
            int strLength = ReadWriteForEncodingUtils.readVarInt(byteBuffer);
            if (strLength < 0) {
                return null;
            } else if (strLength == 0) {
                return "";
            }
            ByteBuffer strBuffer = ByteBuffer.allocate(strLength);
            int varIntLength = ReadWriteForEncodingUtils.varIntSize(strLength);
            byte[] bytes = new byte[strLength];
            channel.read(strBuffer, offset + varIntLength);
            strBuffer.flip();
            strBuffer.get(bytes, 0, strLength);
            return new String(bytes, 0, strLength);
        } catch (ClosedByInterruptException e) {
            logger.warn(
                    "Current thread is interrupted by another thread when it is blocked in an I/O operation upon a channel.");
            return null;
        }
    }

    @Override
    public String getFilePath() {
        return filePath;
    }
}
